Fluid-pressure indicators may be employed in a system to provide an indication as to the fluid pressure of the system. Generally speaking, fluid-pressure indicators can provide a visual indication as to the exact fluid pressure within a system or, alternatively, can provide an indication as to whether the fluid pressure within the system is above or below a threshold pressure.
Fluid-pressure indicators that provide a reading of an exact fluid pressure within a system may be employed in boilers, compressors, and air-supply lines, for example, where delivery of a fluid at a predetermined pressure is required for system performance. Fluid-pressure indicators that provide an indication as to whether fluid pressure is above or below a threshold pressure may be incorporated in a closed-loop system such as a refrigeration system or a hydraulic system for use in determining whether system pressure is at a safe level for repair and/or maintenance.
One such hydraulic system that may incorporate a fluid-pressure indicator is a hydraulic hybrid vehicle system that employs hydraulic pumps driven by vehicle inertia under braking to store kinetic energy as hydraulic pressure. Such hydraulic hybrid vehicle systems typically include an accumulator that stores hydraulic fluid at relatively high pressures (approximately 7,000 psi) that may be used to drive components of the vehicle during use. While generating and utilizing high-pressure hydraulic fluid in a vehicle increases the overall efficiency of the vehicle, such high-pressure hydraulic fluid must first be reduced to a lower pressure (i.e., approximately 100-200 psi) before a technician can perform maintenance on the hydraulic system and related vehicle components.
Conventional fluid-pressure indicators are not suitable for use with a high-pressure, closed-loop system such as the hydraulic hybrid vehicle system described above, as conventional fluid-pressure indicators are susceptible to damage at high-pressure. For example, U.S. Pat. No. 5,189,979 (the '979 patent) discloses a fluid-pressure indicator including a housing (11) having a diaphragm (16), an indicator disk (20), and a sealed envelope of transparent flexible film (26) enclosing an optically dense indicator fluid (27). The diaphragm (16) is exposed to the fluid pressure of a system in which the housing (11) is installed and exerts a force on the indicator disk (20) to compress the sealed envelope (26) and displace the optically dense indicator fluid (27) when the fluid pressure within the system exceeds a predetermined amount.
While the device of the '979 patent adequately determines and displays whether a pressure of a closed-loop system is above or below a threshold pressure, the diaphragm (16) is not sealed relative to the housing (11) and, therefore, should the diaphragm (16) be exposed to high-pressure fluid, the high-pressure fluid would damage the diaphragm (16), indicator disk (20) and/or sealed envelope (26). Namely, the high-pressure fluid would be permitted to flow around the diaphragm (16) and, further, would be permitted to continually apply a force on the indicator disk (20)—directly and via the diaphragm (16)—up and until damage of the various components.
Therefore, further improvement in the art is desirable.